plt.scatter plot 结果是空白

Question

the code below returns a blank plot in Python:

# import libraries
import pandas as pd
import os
import matplotlib.pyplot as plt
import numpy as np

os.chdir('file path')

# import data files
activity = pd.read_csv('file path\dailyActivity_merged.csv')
intensity = pd.read_csv('file path\hourlyIntensities_merged.csv')
steps = pd.read_csv('file path\hourlySteps_merged.csv')
sleep = pd.read_csv('file path\sleepDay_merged.csv')

# ActivityDate in activity df only includes dates (no time). Rename it Dates
activity = activity.rename(columns={'ActivityDate': 'Dates'})

# ActivityHour in intensity df and steps df includes date-time. Split date-time column into dates and times in intensity. Drop the date-time column

intensity['Dates'] = pd.to_datetime(intensity['ActivityHour']).dt.date
intensity['Times'] = pd.to_datetime(intensity['ActivityHour']).dt.time
intensity = intensity.drop(columns=['ActivityHour'])

# split date-time column into dates and times in steps. Drop the date-time column

steps['Dates'] = pd.to_datetime(steps['ActivityHour']).dt.date
steps['Times'] = pd.to_datetime(steps['ActivityHour']).dt.time
steps = steps.drop(columns=['ActivityHour'])

# split date-time column into dates and times in sleep. Drop the date-time column

sleep['Dates'] = pd.to_datetime(sleep['SleepDate']).dt.date
sleep['Times'] = pd.to_datetime(sleep['SleepDate']).dt.time
sleep = sleep.drop(columns=['SleepDate', 'TotalSleepRecords'])

# add a column & calculate time_awake_in_bed before falling asleep

sleep['time_awake_in_bed'] = sleep['TotalTimeInBed'] - sleep['TotalMinutesAsleep']

# merge activity and sleep
list = ['Id', 'Dates']
activity_sleep = sleep.merge(activity,
                on = list,
                how = 'outer')

# plot relation between calories used daily vs how long it takes users to fall asleep

plt.scatter(activity_sleep['time_awake_in_bed'], activity_sleep['Calories'], s=20, c='b', marker='o')
plt.axis([0, 200, 0, 5000])
plt.show()

NOTE: max(Calories) = 4900 and min(Calories) =0. max(time_awake_in_bed) = 0 and min(time_awake_in_bed) = 150

Please let me know how I can get a scatter plot out of this. Thank you in advance for any help.

The same variables from the same data-frame work perfectly with geom_point() in R.

Answer 1

I found where the problem was. As @Redox and @cheersmate mentioned in comments, the data-frame that I created by merging included NaN values. I fixed this by merging them only on 'Id'. Then I could create a scatter plot:

list = ['Id']
activity_sleep = sleep.merge(activity,
                on = list,
                how = 'outer')

The column "Dates" is not a good one to merge on, as in each data frame the same dates are repeated in multiple rows. Also I noticed that I get the same plot whether I outer or inner merge. Thank you.